In the LLVM style guide, we prefer not using braced initializer lists to
call a constructor. Also, we prefer using an equal before the open curly
brace if we use a braced initializer list when initializing a variable.
See
https://llvm.org/docs/CodingStandards.html#do-not-use-braced-initializer-lists-to-call-a-constructor
for more details.
The style guide does not explain the reason well. There is an article
from abseil, which mentions few benefits. E.g., we can avoid the most
vexing parse, etc. See https://abseil.io/tips/88 for more details.
Signed-off-by: hanhanW <hanhan0912@gmail.com>